andmattia
Posts: 12
Joined: Mon Apr 26, 2021 7:40 am

Strange Char on LCD HD44780+Pcf8574

Thu Jun 23, 2022 10:53 am

Hi

I use an LCD HD44780 + Pcf8574 in my raspi and i write data via C# code. All works fine but in some case display show strange char. If i restart application it works fine but after some pressure it happens again.

I read this issue is related to freq that arduino solve with wire.setClock.

I try to set
dtparam=i2c_baudrate=190000 (-> 95Khz)
but if remove my thread sleep LCD show strange char

Any idea?

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FTrevorGowen
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Re: Strange Char on LCD HD44780+Pcf8574

Thu Jun 23, 2022 12:26 pm

andmattia wrote:
Thu Jun 23, 2022 10:53 am
Hi

I use an LCD HD44780 + Pcf8574 in my raspi and i write data via C# code. All works fine but in some case display show strange char. If i restart application it works fine but after some pressure it happens again.

I read this issue is related to freq that arduino solve with wire.setClock.

I try to set
dtparam=i2c_baudrate=190000 (-> 95Khz)
but if remove my thread sleep LCD show strange char

Any idea?
What "E-strobe" timings are in use? You may be falling foul of this known issue (esp. w.r.t. PCF8574 based display interfaces):
http://www.cpmspectrepi.uk/raspberry_pi ... gData.html
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B, B+, and a A+) but Buster on the P3B+, P4B's & P400. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

andmattia
Posts: 12
Joined: Mon Apr 26, 2021 7:40 am

Re: Strange Char on LCD HD44780+Pcf8574

Tue Jun 28, 2022 3:32 pm

Hi Trev

thanks for you reply but how can I check this timing?

In my c# app I doesn't set nothing. I use this sketch
https://docs.microsoft.com/en-us/dotnet ... cd-display

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FTrevorGowen
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Re: Strange Char on LCD HD44780+Pcf8574

Tue Jun 28, 2022 4:20 pm

andmattia wrote:
Tue Jun 28, 2022 3:32 pm
Hi Trev

thanks for you reply but how can I check this timing?

In my c# app I doesn't set nothing. I use this sketch
https://docs.microsoft.com/en-us/dotnet ... cd-display
Sorry I don't use C# so can't comment further however I would expect the timings to be observable in the source code if you have access to that. If you post what may be the relevant parts here within code tags someone else may be able to advise you better.
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B, B+, and a A+) but Buster on the P3B+, P4B's & P400. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

andmattia
Posts: 12
Joined: Mon Apr 26, 2021 7:40 am

Re: Strange Char on LCD HD44780+Pcf8574

Wed Jun 29, 2022 10:51 am

Ok

I try to look to source code on gitHub

thanks for your suggestion

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